Surgical cannula



FIG. 1 is a side elevation of a surgical cannula showing our new design;

FIG. 2 is an elevation as seen from the opposite side of FIG. 1;

FIG. 3 is a front elevation thereof;

FIG. 4 is a rear elevation thereof;

FIG. 5 is a top plan view thereof; and

FIG. 6 is a bottom plan view thereof. 

The ornamental design for a surgical cannula, as shown and described. 